1. Field of the Invention
The present invention relates to an improved manually operable pump for dispensing quantities of a fluid substance in the form of liquids, creamy substances or the like through the hollow operating stem of the pump. The pump enables the substance to be dispensed when in any position while preventing, under normal conditions of use, the passage of fluids (air, gas or liquid) between the outer surface of the stem and the adjacent surface of the hole in the pump ring cap through which said stem extends and is translatable.
2. Discussion of the Background
Many types of manually operable pumps are known for externally dispensing, through the cavity of a stem during its operation, quantities of fluid substances (liquid or creamy) drawn from a container on which the pump is mounted; the hollow stem extends to the outside of the pump body by passing through a hole provided in a ring cap forming part of the pump and defining one end of said pump. The term “ring cap” means any body or element for closing the pump body at one end and for enabling the stem to pass. Known pumps are mounted on containers in which the pressure under rest conditions is substantially equal to atmospheric pressure.
Examples of known types of pumps are those described in detail in U.S. Pat. No. 3,583,605A, U.S. Pat. No. 4,960,230A, EP-B-0301615 and EP-A-1334774, the teachings of which are incorporated herein for reference. DE 1728199A also describes a pump very similar to those illustrated in the four aforesaid patents.
To prevent a vacuum forming in the container when fluid is withdrawn therefrom and dispensed by the pump, a passageway or aperture must be provided in the pump to enable atmospheric air to penetrate into the container in order to maintain the pressure substantially constant therein equal to the atmospheric pressure. In the known art, air passes through a passageway provided in the pump body or between the pump and the ring cap on which the pump is mounted, the air always passing between the outer surface of the hollow stem and the opposing surface of the hole provided in the pump ring cap through which the stem passes.
This is clearly specified in all the aforesaid prior patents, for example in lines 62-67 of column 2 of U.S. Pat. No. 3,583,605A, in lines 2-5 of column 4 of U.S. Pat. No. 4,960,230A, in the last three lines of column 4 and the first two lines of column 5 of EP-B-0301615, in lines 14-22 of column 1 of EP-A-1334774, and in the first paragraph of page 8 of DE 1728199A. The passageway existing between the outer surface of the pump hollow stem and the surface of the hole in the ring cap through which the stem passes presents problems, one of which is that the external air which penetrates into the container can deteriorate the characteristics of the fluid substance contained therein, another being the fact that the fluid can seep or leak to the outside of the container through the said passageway when the container and pump lie in a horizontal position or with the pump facing downwards from the container.
These problems cannot be prevented with known pumps because atmospheric air must be able to enter the container to prevent the pump blocking (and hence no longer usable) if a vacuum forms within the container on dispensing a portion of the fluid contained therein.
In a different embodiment, the fluid substances to be dispensed by dispensers for their use must be contained in containers in which a pressurized gas is also present to normally expel the substances under pressure through dispensing devices acting as manually operable aerosol valves, the opening or closure of which results in dispensing or prevents dispensing of the substance respectively.
However, pumps are also known for dispensing a fluid substance and a pressurizing gas from a container containing the substance and the pressurizing gas hermetically sealed therein. Such pumps have structures which seem similar to those of the pumps commonly used on containers which are not internally pressurized, but which are clearly distinct from them.
Some of these pumps are described for example in U.S. Pat. No. 3,211,346A, U.S. Pat. No. 4,511,069A and GB 1537436A, the teachings of which are incorporated herein for reference.
All these pumps present problems which have made them difficult to use, and in fact have prevented their practical utilization. In this respect, such pumps have substantially a form similar to that of a traditional pump but differ therefrom by comprising a cup-shaped body, the cavity of which is sealed by a ring cap sealedly applied to the mouth of a container in which a fluid substance and a pressurized gas are contained. The cup-shaped body presents a chamber with a hole through which the fluid substance rises into the chamber by the effect of the pressure present in the container. This chamber is bounded by a piston sealedly translatable along the inner surface of the cup-shaped body: a hollow stem connected to the piston emerges from and is sealedly translatable through a hole provided in the pump ring cap. Under rest conditions in which the piston is urged by a compressed spring reacting against the cup-shaped body, the cavity in the pump stem is closed by a unidirectional valve.
When the pump is at rest, the pressurized fluid substance present in the pump interior acts on the piston in the sense of maintaining the pump closed, no hole or aperture or passageway being provided in the pump body which would enable the fluid substance or pressurized gas to come into contact with that upper piston surface distant from that facing the interior of the pump cup-shaped body. The consequence of this is that when such pump is operated to dispense a substance, a pressure must be exerted on the pump stem which is greater than that required to operate the common pumps used to dispense substances not under pressure, in order to overcome the thrust of the spring acting on the piston and to overcome the thrust exerted on the same piston by the pressurized fluid substance present within the pump cavity. Pump operation is hence more difficult the higher the internal pressure in the container on which the pump is mounted, and the smaller the size of the dispensing button mounted on the free end of the hollow stem.